The Darwinian theory of evolution by natural selection has been central to the development of biological anthropology. Early workers tended to explain human diversity in terms of migrations and intermixtures. Mendelian (particulate) inheritance of some features was postulated by showing that the variability of quantitative characters in groups of mixed parentage was greater than that of each parental group (Boas  1938). It was not until immunological and biochemical methods enabled identification of blood groups, abnormal haemoglobin variants, and enzyme polymorphisms that particulate inheritance of such specific traits could be demonstrated (Barnicot, in Harrison 1964). The study of genetic variation within and between human populations, and that of processes of natural selection through effects of isolation, migration and differential reproductive success, have become well established. For example, the changing prevalence of non-insulin dependent diabetes in Polynesians has been attributed to the effects of selection against a genotype which, under less affluent conditions, would have had energy-conserving advantages.